The present invention relates to a method for operating a visual display panel, and in particular, for operating a visual display panel for displaying a character. The invention also relates to a visual display device for displaying one or more characters. Further the invention relates to a shop window comprising the visual display device.
Visual display devices for displaying characters, for example, letters, numerals and the like for presenting information are well known. Such visual display devices typically comprise a visual display panel which is formed by an electro-optical medium sandwiched between a pair of transparent substrates. Typically, one of the substrates carries a plurality of row electrodes, while the other substrate carries a plurality of column electrodes. The row and column electrodes are individually addressable and co-operate with each other and with the electro-optical medium for defining a plurality of pixels in the electro-optical medium. The pixels defined in the electro-optical medium by the respective row and column electrodes are arranged in a matrix having a plurality of rows and columns. By selectively addressing the electrodes, each of the pixels are individually and selectively addressable for selectively forming characters for in turn forming the information to be displayed on the visual display panel. Various electro-optical media may be used in such panels, however, a commonly used electro-optical medium is a cholesteric liquid crystal medium. The pixels defined in such a cholesteric liquid crystal medium are operable in a light transmitting mode when a voltage is developed across the pixel by the corresponding respective row and column electrodes, and is operable in a light scattering mode when the voltage across the pixels is reduced to zero. Pixels operating in the light transmitting mode allow light incident on those pixels to be transmitted through the pixels. Pixels which are operating in the light scattering mode allow light incident on those pixels to be transmitted through the pixels, but the light being transmitted through the panel is predominantly scattered. This will be well known and understood by those skilled in the art.
One problem encountered in the use of such panels for displaying characters, for example, for presenting information is that the contrast between those pixels operating in the light transmitting mode, and those pixels operating in the light scattering mode in certain operating environments may be such that difficulty may be encountered in distinguishing characters displayed from the background against which the characters are displayed. For example, when the panel is displaying characters, such as information or the like in relatively bright ambient light, and in particular, in sunlight where the sunlight is incident on the side of the panel from which the information is being viewed, the contrast between the pixels operating in the light transmitting mode and those operating in the light scattering mode may be insufficient to permit the information displayed on the panel to be easily deciphered.
There is therefore a need for a method for improving the contrast between those pixels operating in the light transmitting mode and those pixels operating in the light scattering mode in a visual display panel which comprises a plurality of pixels which are alternately and selectively operable in a light transmitting mode and in a light scattering mode. There is also a need for a visual display device comprising a visual display panel which comprises a plurality of pixels which are alternately and selectively operable in a light transmitting mode and in a light scattering mode in which the contrast between those pixels which are operating in the light transmitting mode and those which are operating in the light scattering mode is enhanced. There is also a need for a shop window comprising such a visual display device.
The present invention is directed towards providing such a method, a visual display device and a shop window.